Question
An infant’s head sometimes appears to have a bulge that jumps up and down, which is said to be the infant’s fontanelle. How should one determine if an infant’s fontanelle is sunken?
Answer
Under normal circumstances, an infant’s anterior fontanelle should be flat. At birth, the length of the line connecting the midpoint of opposite sides of the anterior fontanelle is approximately 1.5 to 2 centimeters. Subsequently, it gradually ossifies and shrinks, with most infants closing it between 1 and 1.5 years old. If the anterior fontanelle is larger, it may indicate a bone ossification disorder or systemic disease in the infant; while a smaller anterior fontanelle is often seen in microcephaly, which may close between 1 to 3 months and affect brain development. A full fontanelle is usually a sign of increased intracranial pressure due to various reasons and is an important symptom of infant meningitis and encephalitis. As for a sunken fontanelle, it is more commonly seen in infants with acute enteritis or gastritis, or those who have become dehydrated due to vomiting and diarrhea.